I have an Apple Aiport Extreme wifi router and a 2,4 mhz and 2,5 mhz network setup. When I run Istumbler, the SNR value are very low (see attached overview), however, when testing the internet speed (which is cable, max connection speed 70mbits), the average 59,12 Mbps which is fast.

When I try the other channels in my Extreme, the SNR does not change to much and the speed test with speedtest.net so lower download speeds.

Is this something I just have to except? Or can I increase the signal quality? Internet speeds is fine, but then I would expect a better SNR value, or is that not correct?